Fountain pen of the ball point type



Jan. l, 1957 F. RAY

FOUNTAIN PEN oF THE BALL POINT TYPE Filed Nov. 23. 1951 United StatesPatent O FOUNTAIN PEN F THE BALL POINT TYPE Frederick Ray, Montecito,Calif.

Application November 23, 1951, Serial No. 257,728

6 Claims. (Cl. 1Z0-42.4)

This invention relates to fountain pens and particularly to fountainpens of the ball point type wherein the ink commonly used is of veryhigh viscosity which to prevent air locks necessitates that the ink bemaintained in a continuous column from the ball to the air-ink surfaceat the other end of the column. As a consequence, the reservoir must beprovided with an opening beyond the air-ink surface to admit atmosphericpressure to that end of the ink column, and as a result the ink tends toleak out of the opening when this opening is low enough to permit flowof ink by gravity.

Many attempts have been made to overcome this difficulty and one of thecommon expedients is to make the reservoir of small diameter andrelatively long, as it has been found from experience that the inkcommonly used will not leak out of a reservoir which is not overapproximately one-tenth of an inch in diameter. Due to this smalldiameter required to prevent leakage, the quantity of ink that can beheld in the reservoir is not sufficient to supply continuous Writing fora long enough time to be entirely satisfactory. In some instances, toincrease the capacity of the reservoir without increasing the diameter,a tube longer than the holder is used to form the reservoir by foldingit back and forth one or more times so that it can still iit within thepen holder or casing. This construction increases the diiculty andexpense of manufacture and is used little, if at all, at the presenttime. Other expedients have been used, such as an elastic sack, toprovide a larger supply of ink but all are open to one or moreobjections so that most, if not all, ball point pens at the presenttimemake use of a reservoir consisting of a single straight length of smalldiameter tubing.

It is an object of this invention to provide a reservoir of relativelylarge diameter which will maintain a continuous ink column from the ballpoint to the air-ink surface at the opposite end of the ink column andat the same time prevent the leakage of ink from this air-ink surface toand out of the open end of the reservoir.

Referring to the drawings: y

Fig. l is an enlarged diagrammatic View showing in cross-section thecommon type of ink reservoirabove described;

Fig. 2 is an enlarged longitudinal section through an ink reservoircontaining a surface iilm supporter, in accordance with this invention;.t t.

Fig. 3 is a cross-section taken on the line 3-3 of Fig. 2;

Fig. 4 is also an enlarged longitudinal section through a pen having aholder and a removable reservoir and integral ball point, all of whichis commonly designated as the filler;

Fig. 5 shows one modilied form of film supporter in longitudinalsection;

Fig. 6 is a plan view of same;

Fig. 7 shows a second modifiedl form of iilrn supporter in longitudinalsection;

Fig. 8 shows a plan view of same;

Fig. 9 shows a third modified form of lm supporter; and

frice Fig. 10 shows a plan view of same.

The common understanding of the properties of the ink that prevent Howof the ink out of the open end of the reservoir is that the owcharacteristics of the ink prevent this flow out of a small diametertube when one end is closed. In the case of true liquids, which termincludes some inks, viscosity is the only property that could bedesignated by the term flow characteristics. lf the ink has slightplasticity, then the yield point would also be included. Theoreticallyan ink could be made with a high yield point so that it would not owunder gravity through a relatively large tube but such an ink would notflow through the small passages to feed the ball point. As aconsequence, practical inks have low if any yield point and must be usedin a reservoir of small diameter to prevent leakage out of the open end.

I have discovered that the real reason that the ink does not leak `outof the open end of a small ydiameter reservoir closed at the oppositeend is due, not to the flow characteristics, but to the surface tensionof the ink acting in effect as a film stretched across the reservoiragainst which atmospheric pressure is exerted, The opposite end isclosed also by the surface tension acting as a film extending entirelyaround the ball across the opening between the ball and its housing,against which the pressure of the atmosphere is also exerted. Thus, whenthe pen is vertical with the ball uppermost, the pull of the surfacetension around the ball in an upward direction balances the pull of thesurface tension in the reservoir downward plus the head of ink in thereservoir, the atmospheric pressure being the same on the ink-airsurface at the ball as on the ink-air surface in the reservoir.

Since the ink wets the surface of the ordinary materials of which thereservoir would be made, such as iron, copper, brass, glass or plastic,the shape of the surface will always be the same under the sameconditions, that is, same liquid, same diameter and same inclination, sothat it is impossible to increase the critical diameter materially byselection of material of reservoir. Increasing the surface tensionincreases the critical diameter as the square root of the tension butthe surface tension is largely determined by the composition of the inkrequired to meet Writing conditions and very little increase in surfacetension is possible. Specic gravity can not be decreased materially forthe same reason.

The present invention provides a reservoir which has greater freedomfrom the above limitations due to surface tension and specific gravityof the ink. This has been accomplished by providing means in addition tothe reservoir wall for supporting the ink-air surface of the ink at alllevels within the reservoir to maintain the stability of said surfaceand thus prevent leakage along the wall of the reservoir when the openend of the reseivoir is low enough to permit ow of ink by gravity.Several different embodiments of the invention are herein illustrated.

Referring to Figs. 2 and 3, 1 is the ink reservo-ir which may be made ofbrass -tubing 3/16 to 1A inside diameter. 2 is an extension membercarrying the feed channel 3 to the ball 4 (both of usual diameters)which is rotatably mounted in the normal manner in a seat in the end ofthe extension 2. 6 is the novel surface lm suppor-t which, in this case,consists of a helical coil of fine wire preferably of brass or copperabout one half ythe diameter of the inside of the reservoir and having apitch of about 1/16 or less. 7 indicates a support for the helical coil,which support may be in the form of a ring soldered or otherwiseattached to the coil, the outside diameter of the ring fitting snugly onthe inside of the reservoir -to prevent longitudinal movement of thecoil. The number of these supporting rings to be used will depend on thelength of the reservoir, two or three usually being sufiicient to centerthe coil accurately throughout its length. Cuts 8 (Fig. 3) may be madein the outer circumference of the ring to permit the ink to flowtherethrough but are not essential.

c, d, e, f indicate diagrammatically the air-inl surface in thereservoir at any given level, this surface extending from the wall ofthe reservoir to the wire of the coil and across the opening on theinterior of the coil. Thus, due to the adhesion of the ink to the wireof the coil, the inkair surface is supported at a substantially circularzone of about one half the diameter of the outer support at the wall ofthe reservoir. As a consequence, the variation of the pressuredifference across the surface between points of support is greatlyreduced, and this variation can be further reduced by a more complicatedsupport such as could easily be provided by means of a second smallerhelical coil within an outer coil, but l have found that a singlehelical coil support is sufiicient for a reservoir of one quarter inchdiameter, which is about as large as can be used with the ordinaryholder.

Fig. 4 merely shows the usual holder 10 with the reservoir 1 of Fig. 2inserted therein as a filler and with the ordinary cover 11.

Figs. 5 and 6 show a surface lm support 6a also made of a coil of finewire but with the wire coils arranged in concentric relation andconnected by bent portions 6b which space them apart about 1/16. Thedimensions of this modified form of coil may be the same as in Figs. 2and 3 and it may be held in place within the reservoir in the same orany other suitable way.

In Figs. 7 and 8, the surface film support is made up of a series ofcircular plates 9 having cut-out portions 9, leaving cross arms 9bradiating from a small perforated center portion 9C. These plates areheld in spaced relation on a center rod 9d which supports them all as aunit for insertion into the reservoir. Two of the plates, located nearthe opposite ends of the unit, are formed with small radial lugs 9e tocenter the unit within the reservoir. Here, again, the dimensions may beof the same order as those given for the coil unit 6 in Fig. 2. That isto say, the diameter of the stamped out plates 9 may be about one-halfof the diameter of the inside of the reservoir and the spacing betweenplates may be of the order of 1/16. The circular portions of the platesmay be quite narrow or of a dimension similar to the wire coils of theunit 6 or 6a.

In Figs. 9 and 10 the surface lm support is in the form of a tubularscreen 10 arranged within the reservoir 1. and spaced from the reservoirwall by a pair of concentric rings 10a. The mesh of the screen maypreferably be of the order of 1/32. It will be obvious that this screentype of film support will function in the same manner as the other formsabove described.

Even other forms of film support will readily suggest themselves tothose skilled in the art.

What is claimed is:

l. In combination, a tubular ink reservoir for fountain pens of the ballpoint type having an air opening at the end opposite the ball pointthrough which the ink could freely flow and having a cross-sectionalarea greater than that which would permit the ink-air surface lrn to besupported only by the reservoir wall, said reservoir providing an inkcolumn of corresponding cross-sectional area, a film supporting memberimmersed in the ink column and extending throughout the effective lengthof the reservoir, means positioning said member substantially coaxialwith the reservoir and in spaced relation to the reservoir wall, thuspermitting ink flow along the reservoir wall in a directionsubstantially parallel to the -longitudinal axis of the reservoir, saidcoaxial member presenting ylateral and longitudinal openings atsubstantially all levels within the reservoir, said lateral openingspermitting the ink-air surface film to extend through said lateralopenings across the reservoir and thus to receive support at its outerperiphery fromthe reservoir wall and additional support inward of saidouter periphery from the coaxial member substantially continuously fromfull to empty condition of the reservoir.

2. An ink reservoir according to claim 1, wherein the coaxial member isin the form of a wire coil presenting a series of closely spacedparallel thin wire rings located at a multitude of levels within thereservoir.

3. An ink reservoir according to claim l, wherein the coaxial member isin the form of a series of closely spaced circular perforated plateslocated at a multitude of levels within the reservoir.

4. An ink reservoir according to claim l, wherein the coaxial member isin the form of a tubular screen extending throughout the length of theink column.

5. In combination, a tubular ink reservoir for fountain pens of the ballpoint type having an air opening at the end opposite the ball pointthrough which the ink could freely flow and having a cross-sectionalarea greater than that which would permit the ink-air surface film to besupported only by the reservoir wall, said reservoir providing an inkcolumn of corresponding cross-sectional area, and a fixed concentricmember immersed in the ink column and positioned substantially coaxialwith the tubular reservoir and uniformly spaced at its outer peripheryfrom the inside wall of said reservoir, thus permitting ink flow alongthe reservoir wall in a direction substantially parallel to thelongitudinal axis of the reservoir, said concentric member being in theform of a helical wire coil to permit the ink-air surface film to extendacross the reservoir through the spaces between the convolutions of thehelical coil and thus receive support at its outer periphery from thereservoir wall and additional support inward of said outer peripheryfrom the helical wire coil substantially continuously from full to emptycondition of the reservoir.

6. In combination, a tubular ink reservoir for fountain pens of the ballpoint type having an air opening at the end opposite the ball pointthrough which the in'r. could freely flow and having a cross-sectionalarea greater than that which would permit the ink-air surface film to besupported only by the reservoir wall, and means located within the inkreservoir and cooperating with the inside wall thereof for continuouslymaintaining the ink-air surface film substantially intact from full toempty condition of the reservoir, said means comprising a concentric in--sert member uniformly spaced around its outermost periphery from theinside wall of the tubular reservoir and extending substantiallythroughout the effective length of the reservoir, thus allowing theink-air surface film at substantially all levels to be supported at andaround substantially its entire outer periphery by adhesion tosubstantially the entire inner periphery of the tubular reservoir wall,and said insert member presenting axiallyspacedcircumferentially-extending elements having interior and exteriorsurfaces to which the ink-air surface film, inward of its outerperiphery, adheres and from which it receives additional support atsubstantially all levels asV the film extends across the reservoirthrough the spaces between said insert elements.

References Cited in the file of this patent UNITED STATES PATENTS2,208,588 Laforest July 23, 1940 2,504,649 Chesler Apr. 18, 1950 FOREIGNPATENTS 3,958 Great Britain Mar. 14, 1888 813,499 France Feb. 22, 1937571,698 Great Britain Sept. 5, 1945 935,473 France Feb. 2, 1948 130,303Australia Nov. 26, 1948 443,439 Italy Dec. 22, 1948 140,600 AustraliaApr. 3, 1951 806,331 Germany June 14, 1951 274,548 Switzerland Aug. 1,1951 n' "A l'

